1. Field of the Invention
The present invention relates to a cam carrier assembly and, more particularly, to a cam carrier assembly capable of stably supporting an actuator shaft while defining therein a novel oil circuit.
2. Description of Related Art
In a four-stroke gasoline engine, intake and exhaust valves generally serve to control intake into and exhaustion from a cylinder while hermetically sealing the cylinder. Specifically, the intake valve opens in intake stroke to thereby draw a fuel-air mixture into the cylinder, and the exhaust valve opens in exhaust stroke to thereby expel any remaining combustion gas out of the cylinder. In contrast, in compression and power strokes, both the intake and exhaust valves close to thereby hermetically seal the cylinder.
Valve types are divided into, for example, side valve (SV), overhead valve (OHV), and overhead camshaft (OHC) types according to the positions of cam shafts and valves. Among the OHC types, the double overhead camshaft (DOHC) type, with camshafts each dedicated to either an intake or exhaust valve, is generally used in vehicle engines.
The opening/closing of the valve is enabled when a cam on a camshaft pushes one end of the valve with a rocker arm. The camshaft is rotated by a driving force from a crank shaft, transmitted by, for example, a timing chain or a timing belt. A key factor determining the hermetic sealing, the amount of intake and exhaust gases, and so on is a valve lift. The valve lift is a scale representing the distance of a valve face from a valve seat. Generally, an increase in the valve lift leads to an increase in the amount of fuel-air gas drawn into the cylinder through the intake valve and to an increase in the amount of combustion gas expelled from the cylinder through the exhaust valve. Accordingly, intake and exhaust efficiency will increase in proportion to the valve lift.
A Continuously Variable Valve Lift (CVVL) system of the related art includes a control shaft having a control cam, a contact roller integrally coupled with a rocker arm and rotating in contact with a cam of a camshaft, and a swing arm contacting the rocker arm to adjust the valve lift. A cam carrier in the form of a single plate is typically used in order to facilitate assembling a cam or the like to the upper portion of a cylinder head.
A typical actuator shaft is about Φ8, and is subjected to a great amount of stress since it is driven by a motor. Accordingly, the cam carrier is required to adopt a structure for lubricating an actuator shaft and preventing the actuator from being deformed.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.